Mark Zuckerberg, on Thursday, took the unprecedented move of indefinitely banning President Donald Trump on both Facebook (FB) and Instagram. In a blog post, the Facebook CEO said “the risks of allowing the president to continue to use our service during this period is too great.”

Trump’s Facebook and Instagram accounts were blocked on Wednesday following the outbreak of riots at the Capitol by a mob seeking to overturn the results of the 2020 elections, which President-elect Joe Biden won with 306 electoral votes over Trump’s 232.

The attack on the Capitol left four people dead and others injured. Police also disposed of explosive devices found at the headquarters of the Republican National Committee and Democratic National Committee.

Following the outbreak of violence on Wednesday, amid calls to demand his supporters retreat, Trump released a video asking rioters to leave the Capitol, while falsely claiming the election was stolen from them.

In his post, Zuckerberg, who has received considerable criticism for allowing Trump to continue to post fraudulent claims and incendiary rhetoric on Facebook and Instagram over the last four years, wrote that it was clear the president intends to use his remaining time in office to undermine the peaceful transition of power.

“His decision to use his platform to condone rather than condemn the actions of his supporters at the Capitol building has rightly disturbed people in the U.S. and around the world. We removed these statements yesterday, because we judged that their effect — and likely their intent — would be to provoke further violence,” Zuckerberg wrote.

In addition to Facebook, both Twitter (TWTR) and YouTube (GOOG, GOOGL) removed Trump’s message to his supporters on Wednesday for similar reasons. Twitter also stopped users from being able to like or reply to Trumps tweets, and eventually locked his account for 12 hours.

The role of social media companies and their use in the spread of propaganda and false information has been a topic of increasing concern since the 2016 elections during which foreign and domestic actors, were able to spread divisive content with ease with the intent of sowing discord among the American people.

MIT management professor Sinan Aral told Yahoo Finance on Wednesday that social media like Facebook helped mobilize and motivate the Capitol Hill rioters, as well as other acts of violence, including the foiled attempt to kidnap Michigan Gov. Gretchen Whitmer.

“What I’m really concerned about ... is what’s going to happen next, what’s going to happen tonight. What’s going to happen in the next two weeks before the Inauguration, and what is the information role in what happens tonight and in the next two weeks?” said Aral, author of “The Hype Machine: How social media disrupts our elections, our economy, and our health — and how we must adapt.”